LignicolousHyphomycetes from Czechoslovakia 6.Spadicoides andDiplococcium

Seventeen species belonging toSpadicoides Hughes andDiplococcium Grove collected in Central Europe mostly in Czechoslovakia are described and illustrated. Two new species are described inSpadicoides—S. carpatica Hol.-Jech.,S. penatium Hol.-Jech. and three new species inDiplococcium—D. bicolor Hol.-Jech.,D. insolitum Hol.-Jech. andD. parcum,Hol.-Jech.     

Population density of aphids at the time of settling and ovariole maturation inCoccinella septempunctata [Col.: Coccinellidae]

In 1978 and 1979 in Central Bohemia the census of aphid populations on bean, sugar beet, cereals, maize, and alfalfa were taken at the time when overwinteredCoccinella septempunctata L. (1) settled and (2) the ovarioles of females ripened. Settling occurred immediately after aphid immigration. Minimum aphid density required for settling was estimated to about 10 aphids per 1 m² of field area. The aphid density at the time of ovariole ripening equaled 1 aphid per 200–400 cm² of leaf area.     

A lipopolysaccharide fromAspergillus flavus conidia

A lipopolysaccharide was isolated by extraction ofAspergillus flavus conidia with 45 % phenol at 68–70 °C. Quantitative analysis revealed 7 % nucleic acids, 5.5 % proteins, 46 % polysaccharides and 49 % lipids, of which 12 % were covalently bound. Glucose, mannose, galactose and fucose were detected as monosaccharide components of the polysaccharide moiety by gas chromatography; palmitic acid, stearic acid, oleic acid, linoleic acid and myristic acid were mainly present in the lipidic fraction. This material differs from the bacterial lipopolysaccharides, both in composition of the polysaccharide moiety and representation of fatty acids in the lipidic fraction.     

Symbiotic dinitrogen fixation as affected by short-term application of nitrate to nodulatedPisum sativum L.

Effect of nitrate on the nitrogenase (C₂H₂-reduction) activity, growth of nodule tissue accumulation of nitrate and nitrate reductase activity in 4-weeks-old nodulated peas (Pisum sativum l.) was investigated. A relatively slow decrease of the total nitrogenase activity (μmol C₂H₄ per root per h), as compared with plants cultivated without nitrate, was due to both retardation of further growth of the nodule tissue and to a decrease of their specific nitrogenase activity (μmol C₂H₄ per g_f.wt. per h). However, an absolute and pronounced decrease of both nitrogenase activities occurred only 4 or 7 d after the application of nitrate. The addition of nitrate led to its rapid accumulation in the nodule and leaf tissue with a simultaneous induction of the nitrate reductase activity. The nitrogenase activity was not completely inhibited even after a 7-d cultivation with 280 ppm NO₃ ^?-N in the nutrient medium and after accumulation of up to 180 ppm NO₃ ^?-N_f.wt. in the nodule tissue. The results obtained indicate that the “photosynthate deprivation” reflects competition between assimilation of nitrate and fixation of dinitrogen.     

Characterization of dicyclohexylcarbodiimide binding sites in beef-heart mitochondria.

Binding studies with [¹⁴C]-dicyclohexylcarbodiimide showed the presence of binding sites in the beef-heart mitochondrial membrane at a concentration of 1.8 nmol/mg protein (1.4 sites per cytochrome a+a₃). Saturation of these sites correlated with the inhibition of the ATPase activity. The maximum binding capacity could be related with the amount of F₁-ATPase in mitochondria from various tissues.     

Microorganisms in the rhizosphere of wheat colonized by the fungusGaeumannomyces graminis var.tritici

The population of microorganisms in wheat rhizosphere changed in the presence of the fungus Gaeumannomyces graminis var. tritici causing the take-all of wheat. In the majority of cases when the soil was artificially contaminated by the fungus, both the number of bacteria in the rhizosphere and the bacteria/fungi ratio temporarily increased. At the beginning bacteria growing in the presence of NH4+ predominated, later bacteria utilizing organic N-substances prevailed. Pseudomonas fluorescens and the related species colonized the rhizosphere and the soil to a greater extent in the presence of G. graminis. The wheat rhizosphere with G. graminis was found to contain a higher level of the slime-producing bacterium Agrobacterium spp.; this microorganism occurred on hyphal surfaces (in hyphosphere) of both G. graminis growing in soil and Mucor spp. Changes in microbial populations in the wheat rhizosphere during the first stage of colonization by G. graminis can be partly explained by a simultaneous rhizosphere colonization by microorganisms which accompany this fungus in soil. In the period of increase in the number of bacteria in rhizosphere a temporary stimulation of wheat growth was observed.